When Do Snakes Come Out in Colorado? Season, Species, and Safety Tips

Colorado’s diverse landscape — from wide-open eastern plains to rugged mountain foothills — creates ideal conditions for a surprisingly wide variety of snake species. If you spend time hiking, camping, or simply working in your yard, knowing when snakes are active can make a real difference in how prepared and confident you feel outdoors.

You don’t need to fear snakes to respect them. Understanding their seasonal patterns, where they tend to show up, and how to respond if you cross paths with one gives you everything you need to enjoy Colorado’s wild spaces safely. Here’s what you should know about snakes in Colorado throughout the year.

When Snake Season Starts and Ends in Colorado

In Colorado, snakes typically emerge from hibernation in late March or early April, depending on local climate conditions. That emergence marks the unofficial start of snake season, and it continues all the way through the fall months before snakes return to their dens for the winter.

As the days grow shorter and temperatures begin to plummet in late September and early October, most snake species in Colorado start preparing for hibernation. Prairie rattlesnakes, for example, retreat and remain inactive in winter dens from December through February.

As temperatures drop and winter approaches, these reptiles undergo a process known as hibernation, or brumation, which is crucial for their survival during the cold season. Snakes in Colorado usually find a suitable den or burrow to spend the winter months — this can be a rock crevice, a rodent burrow, or even an abandoned building.

Important Note: Even during the transition into hibernation in late fall, snakes are not fully dormant. It’s crucial to exercise caution when encountering snakes during this period. Even though they are less active, they are not entirely dormant, and some species, like the prairie rattlesnake, can still deliver a venomous bite.

So in practical terms, snake season in Colorado runs roughly from late March through early October — about six to seven months of the year. The exact timing shifts slightly depending on elevation and local weather patterns. A warm winter can push emergence earlier, while a cold spring can delay it by several weeks.

Peak Snake Activity Months in Colorado

Not all months within snake season carry the same level of activity. Most snakes are ectothermic, meaning they are cold-blooded and regulate their body temperature using external sources. This makes them avoid extreme temperatures and brings them out to do their hunting in milder conditions.

That behavior creates two distinct windows of elevated activity each year:

• Spring (April–June): Snakes emerge from hibernation in spring and can be more visible during warmer parts of the day when they seek food and mates. According to Fort Collins Natural Areas experts, they are also more aggressive during this time.
• Late Summer and Fall (August–October): During late summer and fall, you may see another flurry of activity as rattlesnakes scurry to find a warm place to hibernate for the winter. During this time, you are more likely to find snakes making their way indoors, or in barns.

Midsummer brings a different pattern. During summer, snakes tend to be more nocturnal, especially during hotter times and extreme heat. On very hot days, you’re more likely to encounter them early in the morning, at dusk, or after dark rather than in the middle of the afternoon.

During mild weather in spring and fall, the prairie rattlesnake is active during the day, becoming more nocturnal during hot summer months. In the spring and fall, cool temperatures require rattlesnakes to bask in the sun or on warm surfaces for much of the day. They often use pavement and other hard surfaces such as trails for basking — this often leads to unfortunate encounters with people.

Pro Tip: On cloudy and overcast days, during the early morning, and the evening are the times you are most likely to encounter a snake out in the open. Plan hikes for midday during spring and fall to reduce your chances of an unexpected encounter.

Common Snake Species in Colorado and Their Active Seasons

Colorado is home to 29 species of snakes found in a variety of habitats throughout the state. The vast majority of these are non-venomous and pose no threat to people. Here’s a look at some of the most frequently encountered species and when you’re most likely to see them.

Bullsnake / Gophersnake

Bull snakes are common and are the largest of the native snakes in Colorado. They can measure up to 88 inches in length and feed on small mammals, birds, and eggs. They are found throughout most of Colorado at elevations below about 8,500 feet. Active from spring through fall, bullsnakes are a welcome presence in gardens and fields because of their appetite for rodents.

One thing to keep in mind: they can mimic a rattlesnake by shaking their tails and hissing, which sounds like that of a rattlesnake. If you encounter a large, hissing snake, take a breath — it’s far more likely to be a harmless bullsnake than anything dangerous.

Garter Snakes

Several species of garter snake call Colorado home. Garter snakes are normally active from March to November and are usually active during the day. The Plains garter snake is distinguished from other garter snakes by the bright orange stripe running down the length of its body. They are found in eastern Colorado and along the Front Range near permanent or semi-permanent sources of water.

You can learn more about the many varieties of these widespread, harmless snakes by exploring the different types of garter snakes found across North America.

Eastern Yellow-Bellied Racer

Eastern yellow-bellied racers are active during daylight hours from April through October. These fast snakes feed on a wide range of prey, from small amphibians and reptiles to small rodents and birds. They are found throughout eastern Colorado and can be identified by their plain brown to olive green or teal color and yellow belly.

Milk Snake

The Central Plains milk snake is an opportunistic hunter, eating a wide variety of small vertebrates. Found throughout Colorado, they adapt well to areas where agricultural activity alters the landscape. These banded snakes are sometimes confused with venomous species, but they are completely harmless. If you’d like to understand the differences between similar-looking species, check out this guide on the difference between milk snakes and coral snakes.

Kingsnake

Colorado’s kingsnakes are active during the warmer months and are remarkable predators. They are known for being immune to rattlesnake venom and will actually prey on other snakes, including venomous ones. To learn more about their diet and habits, see what kingsnakes eat and explore the different types of kingsnakes found across the region.

Key Insight: The vast majority of Colorado’s snakes are non-venomous and actively benefit the ecosystem by controlling rodent and insect populations. Encountering one on a trail or in your yard is a normal part of Colorado outdoor life — not a cause for alarm.

Venomous Snakes in Colorado and When to Watch For Them

Of the nearly 30 species of snakes calling Colorado “home,” only rattlesnakes are venomous. The three types of venomous snakes in Colorado are all rattlesnakes: the Prairie Rattlesnake, the Massasauga Rattlesnake, and the Midget Faded Rattlesnake. Understanding each one — including when and where they’re most active — helps you stay aware without unnecessary worry. For a broader look at venomous species across the country, see this overview of the most venomous snakes in North America.

Prairie Rattlesnake

The prairie rattlesnake is the most widespread rattlesnake species in Colorado and can be found across grasslands, foothills, and rocky outcrops at elevations below 9,500 feet. Most of its activity takes place from April through September. Prairie rattlesnakes retreat and remain inactive in winter dens from December through February.

Rattlesnakes are most active and aggressive in spring and early summer, shortly after emerging from hibernation. Rattlesnake young are born in August through October, which creates another period of elevated activity in late summer as juveniles disperse.

Rattlesnakes are usually very forgiving — they give you every opportunity to stay away before they resort to a venomous bite in self-defense. They don’t chase people; on the contrary, they use their camouflage to avoid being seen and, if unable to hide or slither away, use their rattle as a warning signal.

Midget Faded Rattlesnake

The midget faded rattlesnake is a subspecies of the western rattlesnake and found only in far west-central Colorado. Midget-faded rattlesnakes are typically found near sandstone cliffs and on rocky outcroppings near the Green or Colorado River. The snakes prefer south-facing areas with sunlight and protection from shrubs and ground cover.

Despite its small size — midget-faded rattlesnakes only grow up to about 2 feet long — this species carries a punch. This subspecies possesses the most toxic venom of its group, and it is characterized by the presence of a presynaptic neurotoxin referred to as concolor toxin. If you’re spending time in western Colorado canyons, stay alert on rocky terrain. You can compare this species to others on the most venomous snakes in the US list.

Massasauga Rattlesnake

Massasauga rattlesnakes are much less common and are a species of special concern in Colorado thanks to their declining populations. They are mostly found in southeastern Colorado. The species prefers life below 5,500 feet in elevation. When in their habitat range, a massasauga is usually found in rocky terrain, on sandy hills, and throughout dry, open grasslands.

The venom of the western massasauga is hemotoxic, causing tissue damage and disrupting blood clotting in prey. While potentially dangerous to humans, these snakes are shy and not aggressive, preferring to flee or remain motionless when encountered.

For a deeper dive into how Colorado’s venomous snakes compare to species elsewhere, explore the most venomous snakes from around the world, or read about the most venomous snakes in the US for regional context.

Important Note: It’s easy to confuse venomous and non-venomous snakes in the field. Knowing the difference between venomous and poisonous snakes is a helpful first step. Venomous snakes inject toxins through a bite; no snake in Colorado is “poisonous” in the technical sense.

Where Snakes Are Most Commonly Found in Colorado

Colorado’s varied geography means snakes occupy a wide range of environments. Knowing which habitats they favor helps you stay alert in the right places at the right times of year.

Foothills and Rocky Outcrops

As one Jefferson County Open Space Ranger noted, “We definitely have a rattlesnake belt” — a combination of rocky cover and food sources found in the front foothills, the hogbacks, and the basalt caps of the mesas. These areas are prime rattlesnake territory, especially during spring and fall basking season.

Specific hotspots include Red Rocks, the hogback on the Front Range, Golden, and both North and South Table Mountain. If you’re hiking any of these trails during snake season, stay on marked paths and watch where you place your feet and hands.

Eastern Plains and Grasslands

Venomous snakes can be found in Colorado in open prairies, grasslands, semi-desert shrublands, and forested environments. Prairie rattlesnakes are typically seen along the foothills and the eastern plains and are very common around prairie dog colonies. If you’re exploring the plains, be aware that tall grass and ground-level burrows are common hiding spots.

Western Slope Canyons

Midget-faded rattlesnakes are typically found near sandstone cliffs and on rocky outcroppings near the Green or Colorado River. The Midget Faded Rattlesnake has a more restricted distribution within Colorado, inhabiting the Green River and Colorado River basins in the western part of the state — including counties such as Garfield, Mesa, Delta, Rio Blanco, and San Miguel. Canyon hiking in these counties warrants extra care on rocky ledges.

Near Water Sources

The only species of water snake in the state, northern water snakes are found in northeastern and southeastern Colorado. They have exceptional fishing skills and are found near permanent sources of water. Many non-venomous species — including garter snakes and water snakes — are closely tied to rivers, streams, ponds, and wetlands throughout the state.

Residential Areas and Yards

The prairie rattlesnake is the largest and most common rattlesnake in Colorado and can be found across the state in plains, grasslands, woodlands, and near rivers and lakes. At times these snakes may even wander into human communities like parks and homes as they seek out shady places to escape the heat of the sun.

Snakes like moist areas, dense vegetation, and a lot of hiding areas. By limiting these three factors you can make your home or business less attractive to snakes. Keeping woodpiles elevated, clearing debris, and managing rodent populations around your property can significantly reduce the chances of a snake taking up residence nearby.

Pro Tip: Removing brush piles and rock stacks from your property can reduce attractive hiding spots for snakes. This is one of the simplest and most effective steps homeowners can take during snake season.

What to Do If You Encounter a Snake in Colorado

Coming across a snake — whether on a trail or in your backyard — can feel startling in the moment. But the right response is calm and straightforward. Even snakes considered dangerous to humans are more likely to slither away from you if given the chance and typically only strike when feeling threatened or startled.

On the Trail

1. Stop and assess. When you see a snake, move slowly away from it. If it is going across the trail, stand still and wait for the snake to move away.
2. Give it plenty of room. Follow the “30 by 30 rule” — back up 30 feet and give the snake 30 seconds to get away. If it doesn’t move, turn around and find another route.
3. Never provoke it. A threatened or scared snake is more likely to strike and release extra venom. That means no poking, no throwing objects, and no attempting to pick it up.
4. Watch for coiling behavior. If you see a rattlesnake coiled and/or rattling, that means it’s agitated. Keep your distance. Leave it alone.

If You’re Bitten

Though usually not fatal, a rattlesnake bite can nevertheless be very painful, and it should always be considered a medical emergency. Follow these steps:

• Call 911 immediately. If you are bitten by a snake, call 911 immediately.
• Stay calm and still. Movement increases circulation and can spread venom faster through the body.
• Do not attempt home remedies. Do not ice, use a tourniquet, try to suck out the venom (it doesn’t work), or try to catch and kill the snake.
• Note the snake’s appearance if you safely can. Get medical attention right away. Call a veterinary office or hospital on the way to confirm they have the anti-venom available.

Common Mistake: Many people try to kill or capture the snake after a bite, believing it will help with treatment. This is dangerous and unnecessary. Even dead snakes can “bite” because of a reflex action that closes the mouth, injecting venom. Focus on getting yourself to medical care, not on the snake.

Protecting Your Pets

Dogs are more likely to die from rattlesnake bites than humans due to the difference in body weight. Keep dogs on a tight leash if you’re in rattlesnake country. Dogs roaming free are more likely to be bitten by rattlesnakes than leashed dogs, and more than likely will be bitten on the nose or face from sniffing the ground.

Dressing for Safety

Dress for safety when hiking during snake season. Most bites happen to the hands, feet, and ankles, so wear good-quality hiking boots, tennis shoes, and thick socks. Avoid sandals, open-toed shoes, or walking barefoot. Wear long pants. This simple precaution dramatically reduces your risk of a serious bite.

Snake encounters are a natural part of spending time outdoors in Colorado. With the right knowledge about when snakes are active, where they live, and how to respond if you see one, you can enjoy everything this state has to offer — trails, canyons, grasslands, and all — with confidence and calm. For more on the animals that naturally keep snake populations in check, take a look at animals that eat snakes.